During industrial food-frying operations, solids accumulate in the cooking oil. In high-quality food-frying operations, oil-filtration systems are employed as part of the equipment in order to remove solids from the frying oil and thus prolong the life of the cooking oil.
A variety of filtration systems are used in the food industry. One exemplary filtration system of the sort to which the present invention applies uses automatically replaced filter media and pump pressure to force solids-containing oil from the food-fryer through the filter media. Then, intermittently, i.e., after accumulation on the filter media of a filter cake of solids, the system applies air pressure in a “drying” step to remove as much oil as reasonably possible from the filter cake on the filter media (in order to reduce loss of oil), after which a new portion of filter media is moved into position and the “dried” cake of filtered-out solids from the cooking oil is discarded.
This and other generally similar types of oil-filtration systems for use in industrial food-frying have many advantages. However, certain shortcomings and problems exist related to air in the cooking oil, and it is to overcoming these and related problems that the present invention is addressed.
More specifically, systems such as described above have problems related to the presence of air entrained in the cooking oil. Air in the cooking oil is caused, or made more problematic, by the use of air pressure to drive filtered cooking oil out of the filter cake that has progressively accumulated on the filter media during filtration. During the “drying” phase of operation, in which air pressure is applied on and through the accumulated solids cake and filter media (on which the cake has accumulated) to drive cooking oil from the cake and filter for return to the food-frying vat itself, an air surge eventually occurs as the air breaks through the filter cake. This air surge into the return oil flow increases the quantity of air entrained in the filtered oil returning to the food-fryer and causes potentially hazardous turbulence, even splash risks. Turbulence can be a significant safety problem, considering that most food-fryers maintain cooking-oil temperatures of between about 275° F. and 415° F. Further, turbulence can stir up solids in the fryer which then may attached to the food and affect both taste and appearance. (Such solids are typically removed from the bottom of the fryer by settling to the bottom and being removed by a slow-moving conveyor.) Turbulence can also interfere with proper spacing of food objects being cooked, e.g., pieces of chicken, in the food-fryer.
Furthermore, air in cooking oil, however it might get there, can be deleterious to the food-frying operations. The oxygen content of the air naturally increases oxidation of the oil, and thus causes increased degradation of the oil. In other words, even beyond the turbulence problems referred to above, it is problematic to food-frying operations to have air entrained in the cooking oil, and it would be considered highly desirable to minimize the amount of air entrained in the cooking oil.
Moreover, returning filtered oil from cooking-oil filtration apparatus back to the food-fryer itself without in any way affecting the cooking operations can be problematic. Some possible ways of addressing such problems could involve complex equipment and multiple pumps, but this would increase service requirements and attendant operational costs.
There has been a continuing need for an efficient, safe and simple solution to all of the above-described problems in oil-filtration systems for industrial food-fryers.